Hi Thorsten,
Thorsten Behrens wrote:
On Mon, Jan 12, 2009 at 03:03:02PM +0800, sunyinan wrote:
[...]
Hi sunyinan,
I can't believe that a 1000*1000 image looks the same full-scaled on
a proper inkjet a4 or letter-sized printout. The recommended
size for a4 is 2362x3543 (for a 300DPI resolution) - and there *are*
people out there who (mis)use Impress as a photo album.
Lets take an A4: 11.7 x 8.3 in
Lets take a colour image printed on a home-printer => it will have at
most 100 LPI (actually more like 80-90).
11.7*100 = 1170
8.3 *100 = 830
So, a 1170 x 830 pixel colour image will print optimally on any
home-printer.
Lets take now a professional image-setter with 150 LPI:
11.7*150 = 1755
8.3 *150 = 1245
Any resolution higher than this is NOT useful, as the printer driver or
printer processor will firstly scale down the image and then print it.
In order to construct the various colours, the printer combines lots of
dots, i.e. a 600 DPI will combine at least 6*6=36 dots to create 37
levels of gray (it is similar - though more complex - for colour
prints). Thus, a 600 DPI printer will actually operate as a 100 LPI
device (and usually lower than this, as a 85-90 LPI device). LPI is
relevant, NOT pixels, but device manufacturers do NOT report the (TRUE)
LPIs.
Sincerely,
Leonard
If you agree with it, I think the next step is to find how and
where to descale the high-res image.
When inserting it. You don't want to mess with existing documents,
at least not without asking the user.
Maybe we can provide an option to let the user deciding whether
saving the original size or not when he saving a file.
As pointed out above, definitely.
Cheers,
-- Thorsten
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